To produce hydrocarbons from subterranean reservoirs, oilfield operators drill and case the borehole. When doing so, a shallow portion of the borehole may be cased to protect the water table from possible contamination by hydrocarbons and drilling fluids, whereas deeper portions of the borehole may be later cased as needed to facilitate the drilling process or completion of the well.
Each borehole is typically cased with a casing string, i.e., lengths of steel pipe threaded together and lowered into the borehole before being cemented in place. Despite being made of steel and secured by cement, casing strings can fail. Among the many factors that may contribute to casing failure is internal casing wear. The main cause of such casing wear is the frictional rubbing of other tubular strings on the inner surface of the casing string. For example, as a drill string moves and rotates inside a casing string, it rubs against the inner surface of the casing string, potentially reducing the wall thickness and thereby degrading the casing string's integrity and resistance to deformation.
Operators attempt to anticipate, and account for, casing wear when setting out suitable casing string specifications for each borehole. However, the estimation of wear volume often fails to match the actual measurements. Since these estimations are often inaccurate, they incur excess costs in two forms: overly thick casing walls due to unreasonably high safety margins, and downtime to address failures of casing integrity.